Mining processes involve the transformation of vast amounts of rock in order to extract the valuable metal or mineral. An essential extraction process is comminution, that is the reduction in size by crushing or grinding. Comminution usually requires large machines cost-effectively applying the forces required to comminute the ore. In turn, the machines are subject to large reaction forces. As a consequence, the machines wear. Since large masses of ore are processed, a great deal of energy is required. Thus, the rising costs of energy and of steel, which is used to fabricate the mills, are two factors that are a constant worry for the industry.
The grinding efficiency of semi-autogenous and ball milling depends on the tumbling motion of the total charge within the mill. Utilization of this tumbling motion for efficient breakage of particles depends on the conditions inside the mill. Monitoring to measure the condition inside the mill barrel during operation is difficult due to severe environment presented by the tumbling charge.
It has been possible to contribute to a better understanding of the behavior of these mechanical systems with the advent of prior art discrete element methodology (DEM) charge motion models. The fundamentals behind these models are both very rigorous and sound. Validation of these models in real mills is limited to the measurement and comparison of measurable parameters such as power, throughput and wear. The ball and rock trajectories, the frequency and intensity of collision events (impact and abrasion), the effect of friction on rotation, the roll or slip of the balls and the difference between wet and dry conditions in the mill are all significant aspects effecting the overall frequency of events and the associated effect on breakage and wear that are difficult to evaluate, measure and therefore model and simulate with a view to improve and optimize.
Therefore, there is a need for an information-gathering tool capable of recording events occurring in the mill to study how energy is consumed in a mill and particularly how it is distributed in impact and abrasion energy spectra as well as determine the frequency and intensity of applied forces and moments.